long time no post from me on this forum, mainly due to my 2-year pause in my real bike riding (apart from a few shorter trips).

This year I prepared the bike quite well for the summer trip to Italy, and also had it checked and set (valve clearance, carbs synchro & mixture) by usual garage. They handed the bike back to me with an alert for a strange noise coming probably from the crankshaft bearing, but since it is not quite common for this engine, they would not know exactly.We headed for Italy and had to return back after only 100 kms, since the noise became clearly audible (specially on idle when there is no wind noise).

Until now the bike has been running well, I have it as a 2nd owner from 16.000 kms. Regular and proper maintenance, no load on the engine at all (travel speed 120 kph, sometimes 140kph on highways). Engine oil Castrol 10W-40 only. No problems ever....

Has something similar occured to anyone else? Any tips or clues would be welcome.

This year's season is over for me, since they are not sure whether it would really be the bearing so a thorough analyse would have to be done - and I'm not going to do this in full season where most garages are looking only for the quick change-oil-and-plugs-and-chain operations...

As your garage already told you, crankshaft-bearing-failure is extremely rare in the Bulldog-engine (here in Germany we haven´t heard of any..not one!!)

Now, noises are very hard to convey in writing...what kind of noise is it? If it were the crankshaft-bearing you would not only hear a noise (like a very low "rumbling") but you would also have a noticeable vibration in time with the noise while accelerating..

What else did you notice? When? Standing still or while riding the bike?

thanks for your post. It really seems that either I have an exceptional fault or there is another defect, perhaps much more easier to repair.

Ever since I have installed the TOPHAM carb kit I noticed not only a louder sound from de-restricted air intake but also a bit of noise-waves coming out with the 1/2 frequency of engine speed (give or take). It was only present on idle, but as you say - quite difficult to describe a noise.

And yes, there are some vibrations. In the long past I noticed some vibs around 4000 rpms but I paid no attention to it. Now as the noises became louder (it's also different kind of noise) there are some noticable vibs on the bike and surely it is not OK.

When I have the chance through the weekend I'll try to record it. In the meantime I'm looking through the web to find what could be possibly tuned on the engine

the vibrations around 4.000rpm are "normal"..up to a certain point! By installing the "Topham-Kit" with the correct jets (not bigger than132,5) and removing the stops from the top of the carb-slides, you can now start the fine-tuning of the engine which, in the end should result in the disappearing of nearly all vibrations!

First and furthermost you should check the CO-Emission (not at the end of the exhausts because you have to regulate CO on both Carburators sepparately! As both exhaust come together under the engine, measuring must be done on the pickups on both header pipes..look at my album and you´ll see where) From the factory both carburators come much too lean. Both cylinders should have 4,5% CO minimum!!
When both carbs have the correct setting, you should then sychronise them.

If all this has been done properly, you won´t recognize your engine any more

Cheers

Axman

p.s.: when setting the proper CO% it is mandatory, that you disconnect the AIS!! If you fail to do this, the settings will always be wrong!

I've installed the Topham kit as it comes, i.e. with their jets. The AIS is removed, but I am not sure whether the garage made the last setting according my wish; I too had the impression that the CO setting is quite lean, so I asked them to enrich it a little but pretty sure they had not done it so and kept the factory settings instead.

Anyhow, I found a garage which is willing to take the job in full-season. They'll take their time not only focusing on the cause of noises but also check the engine in general... I may not have the bike for some weeks, but if all goes fine I'll enjoy some september days on 2 wheels. This morning I waved good-bye to the trailer with my Bulldog loaded on it...BTW should the timing chain/wheels be changed on my mileage (60.000 kms) preventionally ? I only heard that the chain is not well dimensioned so it should be changed when there's an opportunity.

in the workshop-specs that every dealership has, it says, that CO should be regulated to at least 4,5% ! We have had engines here, that had under 1%! So tell them specifically what you want

In ref to your question about the timing wheels and chain..: I would´nt touch them!! Here we have never heard of any problems with the timing gear..si if the gears are not worn and the chains are´nt lenghtened..leave them alone

First I intended to record the engine assembled but then I thought - hey, maybe if I make a recording of the disassembled bearing perhaps the guys from the forum advise me whether it makes sense to take the engine apart or not

The garage had found nothing else as a possible source of noises, and compared to the other bearing it makes quite a difference. I'll change both.

It also means for a bike with 60.000 kms: (all evaluation done acc. to factory specifications)
-> clutch still OK
-> gearbox untouched
-> lowest piston ring (the wiping one) does not move really smoothly since it's carbonised a little
-> freewheel (imho the critical component on a BT) runs fine, but no idea how to tell

So apart from the bearings I'll only change the timing chains having the engine already disassembled. There's only little wear on them but the price's OK so why not...

Any ideas what else could be done / improved being so far with the disassembly?

you seem to have found the problem : that bearing really doesn´t sound good anymore..I would change both too. But being so far, I would change the con-rod bearings too..just as a precaution.

How was the compression before you dismantled the engine? If it was ok and you haven´t noticed any blowby on the piston skirts, I would only de-carbonize the ring-grooves and leave it at that. Although...putting an new set of rings on the pistons wouldn´t be a big thing now...

actually I don't have any clue why the bearing's gone. Never pushed the bike's limits, redline only exceptionally, regular oil change (always Castrol 10W-40, although today it doesn't mean much in terms of oil brand). Usually I would drive it between 3-4,5k revolutions. So in my opinion it must have been kind of faulty bearing (though the 2nd one is not 100% either).

I haven't checked the compression before, but since there are no significant burnt traces on pistons below the piston rings I will keep it as it is.

I'll order new bearings tomorrow (the bike is not at Yamaha garage and these parts are bike-specific) and hopefully all will be fine at mid-August.

for an engine that has run 60.000km´s everything - except the main bearings - looks absolutely excellent!A few small scratches on the piston skirts (probably from revving the engine before it is warmed up) are no problem if the cylinders (I coudn´t see the innards properly) are not marred. Even the damaged bearing is not blue from overheating

It cannot be, that they were "overstressed"...my bulldog (from 2002 with 65.000 km´s now) is often used up to its full potential. I once on the Autobahn in summer, as a stresstest, even ran it for nearly 1 1/2 hours at nearly 200 km/h, revved out at redline..! After that I pulled the clutch and stopped at a parking...the engine idled normally as if nothing had happened. This engine seems to be bulletproof...except yours I am sorry to say.

An that´s why we are very much interested to hear from you. Maybe you´ll find a reason for this bearing-failure..a clogged oil-line for example

I just finished the trial run after engine re-assembly and it runs just fine. No weird noises, no vibrations to be felt in the feet Too late for a weekend on a bulldog, but at least I know it's well prepared for next year.

Unfortunately there was absolutely no trace of anything gone wrong in the engine, so I assume it was just a defected batch of bearings or whatsoever. Hopefully next 60.000 km I should be free of such things.

Thanks for the tip with boats.net - it was very quick (at least their part; it took nearly 3 weeks to get it done through customs in CZ). Perhaps I'll send a question to the Yamaha spares Europe just to have a clue why the same part costs 25% when ordered in the US....